Manufacture of slip-resistant paper



July 16, 1963 J. D. HILL ETAL 3,097,989

MANUFACTURE OF SLIP-RESISTANT PAPER Filed Dec. 28, 1959 3 Sheets-Sheet 1 INVENTOR. IL/6h D- H! and BY Dean -J. Cain.

July 16, 1963 J. D. HILL ETAL 3,097,989

MANUFACTURE OF SLIP-RESISTANT PAPER Filed Dec. 28, 1959 3 Sheets-Sheet 2 IN V EN TOR. Justin D. Hill and BY Dean J. Cazn.

J. D. HILL ETAL MANUFACTURE OF SLIP-RESISTANT PAPER July 16, 1963 5 Sheets-Sheet 3 Filed Dec. 28, 1959 INVENTOR. Juslin D. Hill and Deon J. Cain.

ATTORNEYS.

United States Patent Tice 3,097,989 MANUFACTURE OF SLIP-RESISTANT PAPER Justin D. Hill and Dean J. Cain, Lawrence, Kans.,

assignors to The Lawrence Paper Company, Lawrence, Kans., a corporation of Kansas Filed Dec. 28, 1959, Ser. No. 862,374 7 Claims. (Cl. 162-135) This invention relates to the manufacture of paper and paper products, and more particularly to the manufacture of a novel, slip-resistant paper for use in combining same into corrugated fiberboard or paper containers.

Paper packages, containers and the like fabricated from hag papers, kraft papers, corrugated fiberboard and other types of cellulosic materials, as are used for packaging and shipping of various foodstuffs, articles and the like, possess the inherent disadvantage of slipping and sliding against each other when being transported by hand trucks, various carriers and the like, and also even while in storage. This characteristic of the packages or containers results in shifting of loads, toppling of stacks, spillage, damage to containers and the goods therein, and also results in accidents to handling personnel. Attempts have been made to overcome this difficulty as, for example, in the employment of containers treated with a form of adhesive on the outer surfaces, use of creped paper in the fabrication of the container, coating the container or portions thereof with various sprays and other material having friction characteristics, or otherwise treating the paper to provide a less smooth surface. However, it has been found that it is desirable to have smooth calendered surfaces on such papers and containers in order to have satisfactory printing characteristics, and such smooth surfaces tend to reduce moisture absorption and penetration into the papers. The papers and containers variously treated as above are not entirely satisfactory, either for the reasons of economy, poor printing characteristics, insufiicient slip resistance, poor handling characteristics and other reasons depending upon the particular treatment and resulting characteristics of the paper.

The principal objects of the present invention are to provide a novel, slip-resistant paper for packaging articles or for fabrication into board and/or containers that will eliminate the aforementioned difficulties; to provide a process for the manufacture of slip-resistant paper Wherein the paper is treated and has the anti-slip characteristic as it comes from the calender rolls of a papermaking machine whereby the slip-resistant quality is obtained economically and conveniently without additional handling or processing; to provide a slip-resistant paper with a oalendered surface for low moisture penetration and good printing characteristics; to provide a manufacture of slip resistant paper without detrimentally affecting the Mullen test from that normally obtained from substantially the same paper not having the slip-resistant characteristic; and to provide the manufacture of slip-resistant paper in which discrete particles are substantially uniformly dispersed at the surface of the paper during calendering of the paper, and said paper retain its ability to be rolled, combined into corrugated paperboard, or otherwise processed to form containers, packages and the like without loss of the anti-slip characteristic.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein are set forth by way of illustration and example certain embodiments of this invention.

FIG. 1 is a diagrammatic view of a portion of apparatus for making slip-resistant paper in accordance with the present invention.

FIG. 2 is an enlarged diagrammatic view of apparatus 7 3,097,989 K Patented July 16, 1963 2 for treating the paper and applying particles thereto during the calendaring thereof.

FIG. 3 is a perspective view of the water and treatment box.

FIG. 4 is a plan view of the water and treatment box.

FIG. 5 is a rear view of the water and treatment box, with portions broken away to illustrate the structure therein.

FIG. 6 is an enlarged transverse sectional view through the water and treatment box and a portion of a calender roll.

FIG. 7 is a fragmentary perspective view of a four-ply paperboard made in accordance with the present invention.

Referring more in detail to the drawings:

1 designates a papermaking machine wherein fibrous pulp and water is delivered to a beater 2 and is then fed to a Jordan or similar machine 3' where it is further refined. The mixture from the Jordan is delivered toa stock chest 4 from which it flows by gravity or otherwise to cylinders 5, 6, 7 and 8 of paper web forming equipment, said cylinders each having a vat 9 for receiving the mixture. The flow to the vat 9 of the respective cylinders may be controlled by any of the well known means, such as a gate valve (not shown) in the conduits between the stock chest and the vats. The papermaking operation follows the conventional practice wherein the cellulosic fibers are picked up in laminations on the wet felts from which the paper web 11 travels through standard equipment and processes wherein it is moved through the usual presses and dryers. While the process and apparatus illust-rated is for the making of multi-ply paper, the present process is not limited to such multi-ply paper but can be applied to other conventional papermaking processes wherein the paper Web 11 is calendered.

In the illustrated process, the layers of fibers are picked up on the wet felt from which they travel through the usual rolls to the press rolls and dryers (not shown). The layers 11 from the four cylinders are formed in the course of their travel into a single sheet 11 of paper and moved to a calender stack 12 having a plurality of rolls as, for example, 13', 14 and 15, where the layers of the paper are further bonded together by the compressing action of the calender stacks. The paper strip from the calender stack may be rolled or otherwise processed as desired. As in conventional practice, the rolls of the calender stack are urged toward one another to compress the paper strip therebetween, and also said rolls are rotated at different speeds as, for example, the roll 14 is rotated at a slightly faster speed than the rolls 13 and 15, whereby there is a slippage between the surface 16 of the roll 14 and the paper strip 11 as said paper strip moves over said roll. In the illustrated structure, the paper strip is fed over the roll 13 and downwardly and rearwardly over the roll 14, and then forwardly between the rolls 14 and 15.

A water box 17 is suitably supported adjacent the calender roll 14 at the paper outlet or forward side thereof, said water box being an elongated container of a length slightly greater than the width of the paper strip 11 to apply water and material to the calender roll 14 for transmission to the paper strip for the full width thereof, as later described. The water box has a bottom wall 18, end Walls 19 extending upwardly from the bottom wall, and a front wall 20 extending upwardly from the bottom wall and connecting the end walls 19. The rearward edges 21 and 22 of the bottom wall 18 and the end walls 19 respectively are shaped to fit closely to the peripheral surface 16 of the calender roll 14 whereby the roll and the water box walls cooperate to define a trough 23 containing a supply of water and treatment material. In the illustrated structure, a flexible sheet of canvas or the like 24 extends for the length between the end walls 19 with a portion 25 overlying the bottom wall 18 and secured thereto by a batten strip 26, the sheet 24 being of suitable width that a portion 27 thereof extends from the edge 21 of the bottom wall and upwardly therefrom to lie against the periphery 16 of the calender roll 14. The flexible strip preferably terminates below the level 28 of liquid adapted to be contained in the trough 23 as regulated by an overflow 29' which extends through the bottom wall and communicates with a duct 30 for delivery to a collecting tank 31 for recirculation as later described. A baffle member 32 is preferably suitably secured to the upper edge of the water box forward wall 20 and extends upwardly therefrom to serve as a splash baffle to prevent liquid from splashing from the trough forwardly therefrom.

The water box 17 is continuously supplied during the making of the paper with treating material and water through an inlet pipe 33 communicating through ducts 34 with a suitable source of supply, said treating material preferably consisting of granular material such as diatomaceous earth having a particle size of 1 to microns, said particles preferably being of irregular shape with substantially 95 percent passing through a 325-mesh screen. It has been found to be preferable to let the treatment material and water mixture delivered to the water box be of the ratio of 1 pound of said granular particles or diatomaceous earth to 1 gallon of water. As the water and granular particles are delivered and sub stantially maintained at a suitable level in the water box, and the roll 14 rotated in the calender stack, with paper being calendered therein, the water and granular particles are applied to the periphery 16 of the roll 14 and move upwardly therewith as at 35 and are applied to the paper strip 11 as said strip moves between the rolls 13' and 14, and said particles wiped and embedded into the surface 36 of said paper strip as it is being calendered. The particles of diatomaceous earth or other granular material are maintained in suspension in the water box through agitation. In the illustrated structure, the agitation to maintain the particles in suspension is provided by means of air preferably delivered under 30 to 50' pounds per square inch of pressure through a line 37 from a source of air pressure, for example, a motor-driven compressor 38, through a manifold or discharge pipe 39 extending lengthwise of the water box near the roll 14. The air is preferably delivered through a connection 40 approximately midway the length of the manifold, and said manifold has a plurality of jet orifices 41 spaced along the length thereof and directed in opposite directions, preferably in a plane substantially parallel with the bottom wall 18, some of the jets being directed toward the roll 14 and other jets being directed toward the front wall to maintain substantially all of the water and material in the water box in agitation and prevent settling of the diatomaceous earth.

The supply of the water and granular material is preferably provided by mixing water and said granular material, such as diatomaceous earth, in the ratio of 1 pound of diatomaceous earth to 1 gallon of water in a mixing tank 42 provided with an agitator or mixer 43 which is rapidly operated to thoroughly disperse the granular particles throughout the water and maintain said particles in suspension. The mixture of water and particles flows from the tank 42 through a valve controlled duct 44 to a supply tank 45 which has an agitator 46 operating therein to maintain the granular material in suspension in the water. The mixture of water and granular material flows from the supply tank 45 through a duct 47 at a rate greater than is required to supply the waterbox 17, said duct 47 having communication with the duct 34 for delivery of the water and granular material to the water box. A valve 48 is arranged in the duct 34 to regulate the quantity of the material delivered to said water box. The duct 47 has a valve 49 therein which is adjusted to cooperate with the valve 48 to properly proportion the water and granular material between the water box 17 with the excess of the flow being discharged from an open end 50 of the duct 47 into a collecting or return tank 31 which also receives the overflow from the water box 17 through the duct 30. The return tank has an agitator 51 therein to maintain the water and granular material in constant movement and the granular material in suspension in the water. The water and granular material are drawn from the return tank 31 through a duct 52 by a motor-driven pump 53 and is delivered thereby to the supply tank 45 through a duct 54, said pump 53 maintaining circulation of the water and granular material to further aid in maintenance of the suspension of the granular material in the water.

If desired, a size material can be added to the water in the mixing tank 42 whereby it is carried with the water mixture and applied to the paper from the water box 17. It is preferred that a conventional size material be added to the water as it is found that such size material will raise the Mullen test of the paper about 10 percent over the Mullen test of paper not treated with a size material, and while size material tends to give a high gloss finish to the water and make same slicker, it is found that even with the size added to the Water, suspension of granular material as is applied to hard sized calendered board or paper, the discrete particles of diatomaceous earth are dispersed over the surface of the paper and embedded therein whereby the paper surface has a nice, smooth looking finish with good printing characteristics but that the paper is slip-resistant.

It is common practice in testing the slip-resistance of paper to use an adjustable inclined plane having a fixed plate of suitable material such as wood fastened thereto and equipped with an angle-measuring scale. A piece of paper, either the control or treated paper, is fastened in a suitable manner to the fixed plate, and a second piece of paper treated in the same manner is mounted on a slide member as, for example, another plate of suitable material such as steel, which is free to slide on the fixed plate. This second piece of paper and the steel or movable plate are mounted on the paper covered fixed plate when the latter is in a horizontal position. The movable plate is preferably of steel and has a weight of 150 grams or is weighted to provide a total of 150 gram weight therefor. The angle of the inclined plane is gradually and slowly increased until the movable weighted paper begins to slide or move down the inclined plane. The angle at which said movement begins is the angle of slip.

Sheets of hard sized, high calendered kraft paper commonly has an angle of slip of approximately 17 degrees. Bag papers and outer liners of corrugated board that are calendered commonly have an angle of slip of approximately 19 to 23 degrees. With the present process, tests of paper of the same composition and calendered to substantially the same degree, the control or untreated paper had an angle of slip of approximately 23 degrees, and papers treated by an application of diatomaceous earth of a particle size percent of which would pass through a 325-mesh screen and applied to the paper surface at the rate of approximately pound per 1,000 square feet of paper surface had an angle of slip of 33 degrees. It has been found that diatomaceous earth or other granular or siliceous material having irregularly shaped particles of a size to pass through a screen of from 250- to 400-rnesh will provide excellent slip-resistance when applied to the paper surface at a rate of approximately to of a pound to 1,000 square feet of said surface, it being preferred that the rate be approximately .0625 pound per thousand square feet of paper surface, or .0000625 pound per square foot of surface, and when the paper is treated in this manner, it is satisfactory to handle and has good printing characteristics, and when used for covering articles, otherwise packaging of same, or when combined into corrugated board with the treated surface on the exterior thereof, containers made from said board have a slip-resistance as indicated by the above test results and reduce or eliminate the danger of shifting of loads and the like commonly experienced with conventional paper in such packages.

The treatment of the paper is performed during the paper manufacture at the calender stack simultaneously with the calendering of the paper, thereby providing an economical manufacturing process from which the slipresistant paper is obtained without additional handling or processing, the paper sheet, as received from the calendering rolls, having granular particles 55 embedded in the surface 36, as illustrated in FIG. 7, whereby the irregular surfaces of the particles have engagement with the fibers of the paper sheet to retain substantially all of the particles on the paper and thereby prevent said paper from having a dusty appearance which would be present if the particles would separate from the paper. With applicants paper, the particles on the surface are dispersed with spaces 56 therebetween, wherein the exposed paper surface is ample to receive printing ink and thereby provide good printing characteristics.

It is to be understood that while we have illustrated and described certain forms of our invention, it is not to be limited to the specific forms or arrangements of parts herein described and shown except insofar as such limitations are included in the claims.

What We claim and desire to secure by Letters Patent is:

1. A paper sheet characterized by a slip-resistant surface, said sheet being composed of paper fibers with an outer surface, and a deposit on said surface consisting of slip-resistant particles consisting essentially of discrete particles of 'diatornaceous earth dispersed and partially embedded mechanically in said paper, said particles being present on said surface in an amount approximately .0001 to .00005 pound per square foot of surface, said outer surface with the particles partially embedded therein being calendered.

2. A paper sheet characterized by a slip-resistant surface, said sheet being composed of paper fibers with an outer surface, and a deposit on said surface consisting of slip-resistant particles consisting essentially of discrete particles of diatomaceous earth dispersed and partially embedded mechanically in said paper, said particles being irregularly shaped -and of a size to pass through a 250- to 400-mesh screen and present on said surface in an amount approximately .0001 to .00005 pound per square foot of surface, said outer surface with said particles partially embedded therein being hard sized calendered.

3. A paper sheet characterized by a slip-resistant surface, said sheet being composed of paper fibers with an outer surface, and a deposit on said surface consisting of slip-resistant particles consisting essentially of discrete particles of diatonrace'ous earth dispersed and partially embedded mechanically in said paper, said particles being irregularly shaped and of to 1 microns in size and present on said surface in an amount approximately A to of a pound per 1,000 square feet of surface, said outer surface with the particles partially embedded therein being hard sized calendered.

4. A packaging material characterized by a slip resistant surface, said material being composed of a multilayer paper having an outer layer with an outer surface, and a deposit on said surface consisting of slip-resistant particles consisting essentially of discrete particles of diatomaceous earth dispersed and partially embedded mechanically in said paper, said particles being of a size to pass through a 250- to 400-mesh screen and in an amount approximately to of a pound to 1,000 square feet of said surface, said outer surface with the particles therein being sized calendered.

5. In a process of producing paper sheet, the steps comprising, collecting fibers in a web, pressing said fibers into a thin sheet, calendering said sheet to further compress same and smooth one surface thereof, treating said one surface of said sheet at the starting of the calendering thereof by applying to said sheet surface an aqueous suspension consisting essentially of discrete particles of diatomaceous earth at a rate of approximately to & pound to 1,000 square feet of said surface whereby said particles are wiped and partially embedded mechanically into said one surface -by the calendering thereof.

6. In a process of producing paper sheet, the steps comprising, collecting fibers in a Web, pressing said fibers into a thin sheet, treating one surface of said sheet by applying to said sheet surface an aqueous suspension consisting essentially of diatomaceous earth at a rate of approximately A to pound to 1,000 square feet of said surface, said diatomaceous earth being discrete particles of 10' to 1 micron size, and immediately calendering said sheet as it is treated to wipe and partially embed the particles in dispersed relation in said one surface and compress and smooth said one surface.

7. In the process of producing a paper sheet having slip-resistant characteristics, the steps comprising, collecting fibers in a web, pressing said fibers into a thin sheet, passing said sheet between rotating surfaces having different peripheral speeds whereby there is relative movement of one of said rotating surfaces and a surface of the sheet contacting same to wipe and smooth said surface of the sheet, maintaining an aqueous suspension consisting essentially of a quantity of water and diatomaceous earth at said one rotating surface adjacent the contact thereof with said sheet to continuously apply a portion of said quantity to said one rotating surface, said diato maceous earth being discrete particles of 10 to 1 micron size and applied at a rate of to pound to 1,000 square feet of said surface, discharging jets of air into said quantity of water and di'atomaceous earth to maintain an aqueous suspension whereby said particles are dispersed on said one rotating surface and wiped onto the contacting surface of the sheet and partially embedded therein as said sheet surface is smoothed by said one rotating surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,725,647 Kirschbraun Aug. 20, 1929 1,857,497 Clapp May 10, 1932 1,857,498 Clapp May 10, 1932 1,989,709 ONeil Feb. 5, 1935 2,643,048 Wilson June 23, 1953 2,647,069 Stericker July 28, 1953 2,872,094 Leptien Feb. 3, 1959 3,005,727 Stiles Oct. 24, 1961 OTHER REFERENCES Decalite Bulletin F50, The Dicalite Company, New York, 1943, page 2.

Quinn et al.: Diatomaceous Silica in Paper, Paper Trade Journal, March 2, 1944, pages 12, 14, and 16. 

5. IN A PROCESS OF PRODUCING PAPER SHEET, THE STEPS COMPRISING COLLECTING FIBERS IN A WEB, PRESSING SAID FIBERS INTO A THIN SHEET, CALENDERING SAID SHEET TO FURTHER COMPRESS SAME AND SMOOTH ONE SURFACE THEREOF, TREATING SAID ONE SURFACE OF SAID SHEET AT THE STARTING OF THE CALENDERING THEREOF BY APPLYING TO SAID SHEET SURFACE AN AQUEOUS SUSPENSION CONSISTING ESSENTIALLY OF DISCRETE PARTICLES OF DIATOMACEOUS EARTH AT A RATE OF APPROXIMATELY 1/10 TO 1/20 POUND TO 1,000 SQUARE FEET OF SAID SURFACE WHEREBY SaID PARTICLES ARE WIPED AND PARTIALLY EMBEDDED 